Chapter 12: The Cell Cycle
What activates kinases?
the attachment of cyclin
Meiosis produces what?
sex cells=gametes= eggs, sperm
How do the spindle fibers of mitosis elongate and shorten?
they elongate by polymerizing, adding more units of tubulin. They shorten by depolymerizing, removing subunits of tubulin.
How many chromatids are in a duplicated chromosome?
2
How many chromosomes are in a human gamete?
23 chromosomes, half the number of chromosomes in a somatic cells. Gametes are haploid in their chromosomal count.
How many chromosomes are in a human somatic cell?
46 chromosomes, 2 sets of 23 inherited from parents
How much time does a cell spend in interphase, what phases are considered interphase?
90% of its cellular life is spent in interphase. This includes G1, S, and G2. The most time of interphase is spent in S phase
Distinguish between a benign tumor and a malignant tumor
A benign tumor is one that has not spread, a malignant tumor is a tumor that has metastasized throughout the body. It has spread to tissues and impaired organs.
What is the meaning of the word genome? Compare your genome to that of a prokaryotic cell.
A genome is a cells entire genetic makeup. Prokaryotes often have a single DNA molecule, eukaryotes have many DNA molecules that are also extremely long.
What is a kinetochore?
A kinetochore is where the spindle fibers attach to the chromosome.
Through a microscope you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely a____?
A plant cell in the process of cytokinesis
What is a gamete?
A reproductive cell
Name two types of somatic cells in your body
A somatic cell is any body cell that is not a sex cell, for example skin cells and liver cells are somatic cells
A typical human cell contains DNA approximately how long?
About 2m of DNA in length
What is a protein kinase?
An enzyme that activates/deactivates other proteins by phosphorylating them
One difference between the growth of cancer cells and the growth of normal cells is that cancer cells ___?
Cancer cells continue to divide even when they are tightly packed together, they lack contact inhibition.
In the cells of some organisms, mitosis occurs without cytokinesis. This will result with___?
Cells that have more than one nucleus
List two specific cancer treatments and tell how each treatment works
Chemotherapy, inhibits cell division in quickly dividing cells. Radiation, damaged DNA in cancer cells causing them to die and not be able to reproduce.
What is transformation?
Conversion from a normal cell to a cancer cell.
Describe binary fission
DNA replicates beginning at place on chromosome called origin of replication. One origin moves to opposite side of cell, cell elongates. Once the cell is roughly twice its initial size, the plasma membrane pinches inward.
Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to___?
Disruption of mitotic spindle formation
What stages of evolution are considered as we reach the cellular division most eukaryotic cells undergo?
First bacteria with binary fission, then dinoflagellates, then diatoms and yeasts, and then most eukaryotes
A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in what phase?
G1 phase, it has not yet reached S phase where the DNA replicates.
What happens at the three checkpoints in the cell cycle?****
G1 checkpoint is the "restriction point where the cell may enter G0 if it is not large enough. G2 checkpoint is the DNA damage checkpoint M phase checkpoint is checking that all chromosomes are aligned.
What are the three checkpoints in the cell cycle?
G1 checkpoint, G2 checkpoint, and M checkpoint
What are the phases of the cell cycle?
G1 phase, S phase, G2 phase, M phase
What happens in each of the phases of the cell cycle?
G1- the cell grows, S-the cell copies its DNA, G2- the cell grows more, M- the cell divides into two cells. (mitosis and cytokinesis)
At which end do kinetochore microtubules shorten during anaphase? Explain the data that supports where this shortening occurs.
Gary Borisy dyed microtubules during anaphase to determine which end shortened. Those on the kinetochore side of the microtubule shortened, the spindle pole side did not.
Describe what happens to the centrosome during interphase and prophase?
In interphase, the centrosomes replicated and remain together near the nucleus. In prophase, the centrosomes move apart and eventually are at opposite poles for during metaphase and anaphase
What occurs in meiosis? How is the chromosome number of daughter cells different?
In meiosis, the two sets of DNA mix and form chromosomes that then are separated, resulting in cells with 23 chromosomes. Daughter cells have half number the chromosomes. (haploid)
What happens if all the chromosome kinetochores are not attached to the spindle fibers?
It will fail the M checkpoint, the cell cycle cannot proceed if not all chromosomes are attached, mistakes in chromosome separation will be made.
What does MPF trigger? What triggers MPF?
MPF= M phase promoting factor. Signals cell to enter division phase. some particular activities that trigger MPF are the fragmentation of the nuclear envelope, chromosome condensation, spindle fiber formation
What is mitosis? How is it different from cytokinesis?
Mitosis is the division of the genetic material in the nucleus. Cytokinesis is the process of dividing the cytoplasm, forming 2 separate cells.
Describe cytokinesis in a plant cell.
No cleavage furrow forms in the cytokinesis of a plant cell. Vesicles produced by the golgi apparatus during telophase line up in the middle of the cell and form a cell plate. Eventually this separates the cells and they have their own plasma membrane. A cell wall then arises between the two cells.
What is anchorage dependence and how does this relate to cancer cells?
Normal cells display anchorage dependence, meaning to divide they must be attached to something such as extracellular matrix or a culture jar. Cancer cells do not require this and can grow and divide without anchorage.
What is density-dependent inhibition and how does this relate to cancer cells?
Normal cells show contact inhibition/density dependent inhibition. This means that when they sense other cells near them and that cells are crowded, they stop growing. This is a behavior that cancer cells do not posses. Instead cancer cells grow out of control with no regard to how many cells are near them. They crowd each other and grow on top of one another
What are growth factors? How does PDGF stimulate fibroblast division?
Proteins released by certain cells that stimulate other cells to divide. PDGF is made by platelets, it binds to fibroblast receptors and allows cells to pass G1 and divide.
Name the two types of gametes
Sperm and eggs
Where do spindle microtubules assemble? What is another name for this place?
The centrosomes. Also referred to as "the microtubule organizing center"
At what end do microtubules shorten in anaphase?
The kinetochore side (by the chromosome) not at the pole
What is the G0 phase?
The non-dividing stage cells are sent to when they fail their G1 checkpoint. Can be called back from this phase to enter division again.
What happens in G2 of interphase?
The nuclear envelope is still present. Two centrosomes have formed. Chromosomes were duplicated in S phase, have not yet condensed in the cell
What is metastasis?
The spread of cancer cells throughout the body, away from original site. Usually involves angiogenesis, a tumor creating its own blood vessels and invading the blood stream of the person, traveling to other locations in the body.
What are the components of the mitotic spindle? What is the source of these components?
These begin to form in prophase. They are fibers of microtubules and associated proteins subunits of tubulin. These come from microtubules of the cytoskeleton that disassemble.
The activity of cyclin-dependent kinases (CDks) rises and falls. Why?
They change with the concentration of cyclin.
Describe cytokinesis in an animal cell
a contractile ring contracts, causing the cleavage furrow to deepen. It continues until the cell pinches into two.
What is an aster?
a radial array of short microtubules that extend from the centrosomes during mitosis
What is the metaphase plate?
an imaginary line in the middle of a cell that all of the chromosomes line up at in metaphase
What is the shortest stage of mitosis?
anaphase, it takes only a few minutes
What happens in anaphase?
cohesion proteins between sister chromatids are broken, chromosomes becomes fully fledged chromosomes. microtubules pull chromosomes to opposite poles, the cell elongates.
How does MPF switch itself off?
during anaphase, it initiates a process that destroys the cyclin attached to it.
What are the components of the mitotic spindle?
fibers made of microtubules and associated proteins
How many chromosomes do you inherit from each parent?
half from each parent. in humans 23 from each parent.
Define sister chromatids, what connects them?
identical copies of the original DNA, joined along their lengths by protein complexes called cohesions. attached most closely to each other at their centromeres.
By what process are eggs formed?
meiosis
Which process reduces chromosome number of daughter cells?
meiosis
By what process are damaged cells in a wound replaced?
mitosis
By what process does a zygote develop into a multicellular organism?
mitosis
In which process are identical daughter cells produced?
mitosis
Which cells do not divide at all in a mature human?
muscle and nerve cells
How many chromosomes do prokaryotes generally have?
one
What happens in metaphase?
the centrosomes are at opposite poles, chromosomes line up in the middle of the cell, microtubules are attached to kinetochores.
What happens in prophase?
the chromosomes condense, nucleoli disappear, two identical sister chromatids are joined at their centromeres, mitotic spindles begin to form, centrosomes move away from each other.
Define chromatin
the complex of DNA and proteins that make up chromosomes.
What are some key roles of cell division?
the continuity of life, developing an organism from a single cell, renewal and repair of cells
The decline of MPF activity at the end of mitosis is due to____?
the degradation of cyclin
What is meant by the cell cycle?
the life of a cell from the time it is formed to the time when it divides into two
Explain the difference between kinetochore and non kinetochore microtubules?
the kinetochore microtubules attach to chromosomes and move them towards poles. nonkinetochore microtubules are responsible for elongating the cell during anaphase.
What phase are most of your body cells in?
the non-dividing state of G0
What happens in prometaphase?
the nuclear envelope disappears, microtubules invade the nuclear area, chromosomes are more condensed, each chromatid has kinetochore for microtubules attach to.
What happens during telophase and cytokinesis?
the two daughter nuclei form, the nuclear envelope arises in each cell, the chromosomes become less condensed. the spindle microtubules depolymerize. during cytokinesis the cytoplasm divides and the cell pinches into two
By what process does prokaryote reproduction occur?
through binary fission, not mitosis
What is the function of non-kinetochore microtubules?
to elongate the cell during anaphase
What is the function of associated proteins in the chromatin complex?
to maintain the structure of the chromosome and help control the activity of the genes
Explain the experiment that provides evidence for cytoplasmic signals
two cells in different phases of the cell cycle were fused to form a single cell with two nuclei. if one of the cells was in s phase and the other was in g1, the g1 nucleus immediately entered s phase. indicating a signal in the cytoplasm controls this process.
When does anaphase begin?
when the enzyme separase cleaves the cohesion between the sister chromatids.